Fixed misreported error codes and elaborated
Fixed misreported error codes and elaborated

Documentation mixed up 406 and 405 error codes, this corrects that

Also elaborated on the possible ways you can receive a 405 error code

See spec test: https://gitlab.com/powisj/gitlab-ce/blob/master/spec/requests/api/merge_requests_spec.rb#L848

axilleas/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq